A Combination of Factors
by Regency
Summary: (Spoilers for BJB.) Things don't turn out as anyone expected. Mark and Bridget make another go of it, Jack doesn't go anywhere, and they're all surprisingly happy with this arrangement. Jack is going to have to revise his personal equation for love. He might have overlooked a variable. OT3 polyamory negotiations.


Author: Regency

Title: A Combination of Factors

Pairing: Mark/Bridget/Jack

Rating: Everyone/G

Warnings: None

Summary: Things don't turn out as anyone expected. Mark and Bridget make another go of it, Jack doesn't go anywhere, and they're all surprisingly happy with this arrangement. Jack is going to have to revise his personal equation for love. He might have overlooked a variable.

Prompt: What happen when Jack starts working on a equation for a compatibility test for 3?

Author's Notes: Come flail with me on Tumblr at sententiousandbellicose. You can prompt me things if you don't mind waiting!

Disclaimer: I don't own any characters recognizable as being from any incarnation of the Bridget Jones series. They are the property of their actors, producers, writers, and studios, not me. No copyright infringement was intended and no money was made in the writing or distribution of this story. It was good, clean fun.

* * *

Mark came out of the bathroom from his post-work shower to find Bridget scrolling through Amazon wearing a pronounced frown. He scrubbed a towel over his dripping hair.

"What are you doing?"

"Ordering a dry-erase board. I thought we'd have at least a few years before someone started writing on the walls."

Mark stepped out of the bedroom into the front room, only to immediately step back inside looking bewildered. "Oh, dear."

"Yup."

He joined her on the bed so they could browse together. Two heads might be better than one on this one.

* * *

Bridget pushed Mark into the main room while she went to deal with William just woken for his 9 pm feeding. Mark was still damp but he'd at least managed to get into something comfortable before he was abandoned to confront their wild-eyed friend alone.

Jack had made their place a regular way station on his Qwantifying Love World Tour. Each time he was in the UK, he bypassed the nearest five-star hotel to sleep on Bridget's old lilo bed. He never seemed to mind and neither did Mark's small family. Jack was just another member of the family come to visit.

Mark approached the agitated younger man carefully. Jack was scribbling a cramped jumble of mathematical symbols on a formerly blank expanse of wallpaper.

"Everything all right, Jack? You're looking frantic."

"I think I forgot something."

Mark rubbed Jack's shoulder in solidarity. "Is it something I can help you with? I'm no mathematician but I've been called clever enough in most instances."

Jack squinted at the wall and then jotted something else down. It was all Greek to Mark. Jack mumbled, "There's a variable I've left out. A factor I forgot to account for when quantifying love." Jack had told the truth when he said that maths were his first love. Jack didn't have much family and he'd had fewer friends as a young man growing up brilliant in the States. His own efforts at finding love in the wild had been disastrous or lackluster. The Qwantifier had been his answer to the all-consuming question of whether he was unsuited to be loved.

"What factor is that?"

"The ability to love multiple people at once."

Mark scratched his jaw thoughtfully. "I'm sure it's not that bad."

"It's bad. It changes everything."

"So what are you saying?"

"I'm saying my algorithm for love is wrong."

"Is it wrong, or is it simply incomplete?" Mark posed.

"I don't know," Jack said. And he appeared truly distressed at this realization.

"Let's bring Bridget in, then. She's got a fascinating way of simplifying difficult situations."

He guided Jack to his and Bridget's bedroom. Mark was going to need back-up.

* * *

He pushed Jack toward the bed where Bridget had been pretending not to overhear everything they said while he logged on to his laptop. He joined them on the mattress and queued up the Qwantifier website. Jack needed to trust his maths again, but that would also mean confronting its shortcomings.

Bridget re-positioned an unusually pliable Jack until he was trapped snugly between them. Mark had the good sense to leave her to her machinations. When she produced a pint of ice cream from a small ice chest beside the bed, he chose not to ask any questions. _Always prepared for an emotional crisis, that one._

"I put myself and Bridget into your Qwantifier and it listed us as being only 7% compatible."

"Which is obvious rubbish," Bridget intoned from his far left. She shushed Jack at the pained noises he made.

"I also put Bridget and yourself in." Mark pulled a face. Jack already knew the outcome, having tried it himself.

"97%."

"To a man."

"That's not _that_ weird. Jack and I have a lot in common." She kissed Jack's cheek. He smiled a little. Mark was relieved. Jack had calmed down considerably from his absentminded professor fugue.

"You're both very spontaneous. Very fun-loving. Outgoing. Attractive. High emotional intelligence." Both the sort of people in whose company Mark thrived rather than those more like himself: taciturn, introverted, pragmatic and highly analytical.

"Am I that attractive, Mark?" Jack rested his head on Mark's shoulder to flutter his eyelids at him playfully. Mark smiled a bit. Jack wasn't the first person to intimate that Mark had more than tolerance for Jack, given how well they got along after William's birth. Mark had been inclined to like Jack before they met; now that there was nothing to lose, he lacked a reason to resist his natural inclination.

"Yes, I suppose you are."

Bridget gave them both a look between mouthfuls of melting ice cream. "Did you try doing you two?"

Jack shrugged and took over for Mark at tinkering with the terms of the compatibility match. He obviously knew more about manipulating his own system than Mark did. "I didn't try it. I was competing with him, not hoping for his hand in marriage."

"Alas polygamy is frowned on by the courts," Mark contributed. "If only we lived in Utah."

"So do it now. You know both of us, Jack. Just put in Mark's vitals stats and see if you're compatible."

"To prove what?"

"To prove the algorithm already works."

"And if it doesn't?"

"If it doesn't, which I think it will, we fix it."

"It's not that simple."

"Not until you do it, it's not." Seeing both men not moving, Bridget grunted in annoyance and swapped Mark's laptop for her ice cream. "Don't eat all of it. Men, I swear." She skimmed over everything Jack had input, made a few minor changes, because she had known Mark Darcy _a long time_ now and the details could make all the difference. "There."

She hit _Match_ and they waited.

The longest two minutes since she took her pregnancy test.

* * *

The three of them stared at the results in variously held silence. Bridget blew her hair out of her face. She hadn't seen that coming; a bit of compatibility sure, but wow. Mark's expression had turned unreadable. Jack was glaring at the screen. _Ask a silly question…_

100%

Somehow Mark Darcy was the perfect unbalanced force to stop Jack's object in motion in its wayward tracks. Huh. That was…interesting. Fascinating. Slightly alarming.

"Well."

"Ditto."

"Works on paper."

"Does it really?" Bridget offered. She had met them both, adored them both. Two more different men would be difficult to find. And yet the friendship had bloomed from almost nothing.

"He's still here," Mark retorted.

"I haven't killed him," said Jack.

"Something clearly works."

"You're very cool about this," opined Bridget once more, giving her rather staid fiance a curious once-over. Not that Bridget thought Mark would be opposed to being compatible with a man. He'd never expressed feelings about it one way or another and, since Bridget was not a man, she hadn't had a reason to think about it.

"We got along just fine until we realized we loved the same woman. It doesn't shock me that we might have other things in common."

"It seems like you have everything in common."

"Including you. We both love you. That has to account for something."

Bridget didn't _mind_ per se, it was just interesting to think about. She and Mark went awfully on paper, and yet unquestionably loved each other to extremes. She and Jack matched well on paper and their mutual affection was genuine but different. Mark and Jack, on paper, had it all, and Mark had said it himself: everything he loved in Bridget he found attractive in Jack. It was telling and she wasn't sure either man realized how much so.

"He's right." Jack retrieved the computer from Bridget's slack hands. "Think of it as a kind of nesting compatibility. You like me because you like her."

"I don't think that's it. I liked you before we met." Mark's job had made him a decent judge of character in professional matters; personal ones, less so. Jack was the sort of man he was likely to have run into in philanthropic circles eventually. He'd looked forward to it.

"Yeah?" Jack queried.

Mark blinked."Naturally. You're impressive."

"So are you."

They shared a grin of mutual admiration.

"Should the ice cream and I leave you two alone?" Bridget had retrieved what remained of her pint of Phish Food once Mark had absently consumed half of it, and Jack another quarter. Their growing sweet teeth were entirely her influence.

"I don't know. I can't speak for Jack, but I'd rather you stayed."

Jack shot Mark a questioning look but Mark was watching Bridget to see if they were on the same page.

She finished a last spoonful of ice cream and returned it to the cooler.

They were very much on the same page.

Now to get Jack in the same book.

* * *

Jack returned to the sitting area several hours later to make some corrections to his equations. He was down to his bare feet and bare chest. His skin was still warm from the duo of bodies that had fallen asleep on each side of him. His thoughts were much quieter this time.

He wrote for a while longer, his calculations more adventurous but aimless. Was an algorithm for polyamory–that was the word he wanted–just a series of individual compatibilities? Could he quantify those attachments with the same pinpoint accuracy? He knew deep down that it wasn't the math that was bothering him, anyway. It was what the math could tell him. Bridget and Mark were his matches, in this configuration. He wasn't unsuited to be loved, but what if love wasn't enough? What if they were his only shot and it still didn't work? Could he take that?

He rested an arm alongside his notes to stare at them more closely. They made some sense. The math was good, sound, to his standards and nothing less. That was comforting Numbers didn't lie. People did.

But these people were different. He wanted them to be the exception.

* * *

Mark left Bridget dozing in bed to check on Jack again.

"What are you concocting now? It's late."

"I had some new ideas while I was asleep. I tried not to wake you."

"You didn't. I had some work to do." Mark grimaced. "I still have some that needs doing. It'll keep. What's on your mind?"

"I'm still making sense of this."

Mark joined him at his ad hoc dry-erase board. He hoped in vain that it would wash off. "Numbers can't account for everything."

"Numbers are what I know. If they can't account for us, how do I trust that it won't…fall apart?"

"You get to know us, get to know _me,_ and then you take a leap of faith."

Jack ran a hand through his disheveled hair. "I thought you were the last bastion of logic in a mad world."

"I am. I've just accepted that in order to live happily I've got to be a little mad myself from time to time." Mark crossed his arms to give Jack some space to maneuver. If Jack felt backed into a corner, this would fail. There was little Mark would hate as much as that. Jack had stayed after William was born. He'd slipped into their routine, into their good graces like the friend he was and then stayed until it wasn't just friendship keeping him there. It couldn't be. But Mark couldn't have that epiphany for him. Not even England's top human rights barrister could make him feel something he had no desire to feel.

"Jack, I've been all over the world and encountered many cultures. Monogamy is not the universal standard. It's not the _only_ way to love."

Jack mirrored Darcy's folded-armed stance.

"It's not…you know, I've always thought of myself as open-minded. I've never cared much about gender. I've never cared much about anything. It's attraction that matters. I'm not even that hung-up on how many people are involved. It's just never been me. I've never felt like this about anybody, much less more than one 'anybody.'"

"No one is asking you to compromise what you feel or feign something that isn't there. This only works if we all agree, if it's something we _all_ want. That means that you're a part of William's life. The three of us all come together. But Jack, you don't lose us if you don't want this. We wouldn't want to lose you." Mark had through some combination of flattery and panic been selected as the spokesperson of this little endeavor, and he was feeling much less than equal to the task.

Jack clutched his marker in his hand till it pinched his palm. "You've spoken to Bridget about this?" This wasn't theoretical. This was real, for all of them.

"I don't think it's violating any rules of the marriage bed to say she brought it up first. You could say she laid it out for me. We fit together, the three of us, together and in our many configurations. We all love William. You and I love her. She loves us both."

"In different ways."

"In ways that are no less important for the distinction."

"And how do you feel about me?"

"Curious. Intrigued. You're an intelligent man. My tastes have always run toward intellect. And of course free-spiritedness."

"Opposites attracting."

"And igniting a lifelong flame. It could happen again very easily, given time."

* * *

Jack didn't really know how to be a part of something like _this_. This was a family, not a one-night-stand. There were bonds and ties, and roots that came with that. Jack wasn't really a roots kind of guy.

"How long?"

"The rest of our lives, perhaps."

That was the wild thing, that Jack was considering it. There wasn't anything substantial tying him to the States that couldn't be transferred to England. Qwantier HQ went where he went. He could make this, _them_ a reality.

Bridget knocked on the doorway to the front room to catch their attention. She was dressed down to her softest pajamas. Jack still remembered how her skin felt against his. How he enjoyed watching her sleep. Loving her would be easy.

"I think what Mark means to say is come back to bed, Jack. It's getting late."

"I should finish this equation." It was a nonsense sequence, something to keep his hands busy while his mind worked. Something neither were likely to realize.

Bridget wrapped herself around Mark from behind and peered worriedly at Jack. "Sometimes there isn't a perfect equation or algorithm, sometimes people just work."

"Like us?" he prompted.

"Like us," Mark confirmed.

"Come to bed," Bridget said again, sincerely.

Jack put down his marker where he stood and went to bed with the people he was going to fall in love with any day now, if he hadn't already.

* * *

The next morning, Jack saved his progress in pictures and scrubbed the Qwantifier's base equation from the wall (most of it; he was going to have to invest in a can of fresh paint). For now. He used the newly arrived dry-erase board to start teaching William about imaginary numbers instead.

William spent most of the lesson trying to eat his fingers, but Jack didn't mind. There'd be time enough for learning when William was older. Jack intended to be there every step of the way.


End file.
